[FIXED] How do I get all elements of Hashmap key and values outside while loop

Issue

I have a query where I retrieve DB values like:

public HashMap<String,String> getStateCapital(String Country) {
    
    HashMap<String,String> c1 = new HashMap<String,String>();
        
    String query = DB query+Country;
        
    try {
        Connection db = DriverManager.getConnection(URL,Username,Password);
        Statement st = db.createStatement();
        ResultSet rs = st.executeQuery(query);
        while(rs.next()) {
        
            c1.put("StateName",rs.getString(3));
            c1.put("CapitalCity",rs.getString(4)); 
           
            System.out.println(c1);                // First c1 output
        } 

        System.out.println(c1);                    // Second c1 output
    
    }
}

Here when I print the first c1 I get HashMap<key,value> Output as

{StateName=Karnata, CapitalCity=Bengaluru}
{StateName=Kerala, CapitalCity=Thiruvananthapuram} 
{StateName=Telangana, CapitalCity=Hyderabad} 
{StateName=TamilNadu, CapitalCity=Chennai}
etc...

But when I print the second c1 I get HashMap<key,value> Output as

{StateName=Karnata, CapitalCity=Bengaluru}

How do I retrieve all the HashMap<key,value> like the first c1 Output outside while loop?

Solution

Consider that Map is a list of entries. Each entry is composed by a key and a value. The key inside is unique, then the value is overridden every time you put the same key.

You can resolve to create a class that represents the state.

public class State {
    private String stateName;
    private String capitalCity;

    public State(String stateName, String capitalCity) {
        this.stateName = stateName;
        this.capitalCity = capitalCity;
    }

    public String getStateName() {
        return stateName;
    }

    public String getCapitalCity() {
        return capitalCity;
    }
    
    @Override
    public String toString() {
        return "State{" +
            "stateName='" + stateName + '\'' +
            ", capitalCity='" + capitalCity + '\'' +
            '}';
    }

}

And you can fill a list of State in order to avoid overriding.

public HashMap<String, String> getStateCapital(String Country) {

    List<State> states = new ArrayList<>();

    String query = DB query + Country;

    try {
        Connection db = DriverManager.getConnection(URL, Username, Password);
        Statement st = db.createStatement();
        ResultSet rs = st.executeQuery(query);
        while (rs.next()) {
            states.add(new State(rs.getString(3), rs.getString(3)));
        }
        System.out.println(states);
    }
}

Answered By - frascu
Answer Checked By - Timothy Miller (JavaFixing Admin)